The control and diagnosis of a vehicular internal combustion engine is typically carried out by a central microprocessor-based controller in response to numerous input signals representing various engine operating parameters. The various input signals are developed by individual sensor devices, and each such signal is ordinarily communicated to the central controller with a dedicated conductor or conductor pair. Since this arrangement obviously requires a large number of wires and controller input ports, what is needed is a more cost-effective way of communicating the required data.